The present invention relates to a container intended for contents under pressure and comprising a liquid and a gas. The invention also relates to a method for the manufacture of such a container.
Pressurized products, such as e.g. beer and refreshing beverages, are packed in most cases in glass bottles or in sheet metal drums. Both of these types of packages are relatively expensive to manufacture and, moreover, have the disadvantage that the containers must be filled individually, which means that they cannot be filled completely, but that an air pocket is formed in each packing container. These air pockets not only mean that the volume of the package cannot be fully utilized, but in most cases also a detrimental effect on the packed product is exercized by the oxygen of the air enclosed in the packing container acts as an oxidant. Since filled containers of the type mentioned here often have long storage time the oxygen gas enclosed in the container is liable to oxidize the flavor substance of the packed product. Consequently, the quality of the product deteriorates.
Thus a need exists for an inexpensive and wholly filled package for pressurized contents, and in the following specification a container will be disclosed which can satisfy this need. The container in accordance with the present invention is characterized by two compression-moulded shell-shaped parts of sheet metal facing one another and being joined to one another. Both parts are moulded from one and the same sheet and both have plane flanges around the moulded shell-shaped portions. The insides of the said parts are provided with a thermoplastic lining by which the flanges are sealed to one another in a first sealing joint. The flanges moreover are joined to one another mechanically in a second sealing joint in that the flanges sealed to one another are folded down against and sealed to the moulded parts of the container and/or rolled together or beaded together under pressure.
The invention also relates to the method of manufacturing a container in accordance with the invention. The method is characterized in that a web of sheet metal, e.g. sheet iron (black sheet), which at least along one of its sides is covered with a thermoplastic lining, e.g. polyethylene, polypropylene or polyester, is provided with at least two folding indications along the central portion of the web. The indications are parallel with the web and with each other and the areas of the web on both sides of the folding indications are compression-moulded with simultaneous stretching of the moulding material to obtain shell-shaped cavities situated right opposite one another on the web. The web is folded along the folding lines in such a manner that its non-moulded edge zones are brought together and sealed to each other by surface melting of the thermoplastic lining of the web within the joined edge zones, thus forming a tube of triangular cross-section, the compression-moulded shell-shaped cavities facing one another in pairs. The contents are introduced into the tube formed by a filler pipe passed into the tube, and that, after filling, the tube is fully pressed together and sealed along the non-moulded portions. The tube is divided up into individual containers by cutting or punching through the web in the area between successive containers, and the flanges around the filled cavity of the container are folded in against the container body, rolled or beaded.